This proposal deals with the hypothesis that there are some impairments in brain-pituitary function during aging in female mice and rats which are dependent on ovarian steroids or functions. We will examine select macromolecular, physiological, and morphological parameters of brain and pituitary to see which show progressive impairments during the course of reproductive aging and which changes are arrested by ovariectomy. We will also investigate if there is a limit to the number of ovarian cycles which is determined by extra-ovarian loci and which may be independent of chronologic age.